Providing desired amounts of blood plasma from whole human blood and subsequently preparing the sample for use in a colorimetric assay of blood constituents has been accomplished in prior devices by either using separate devices and processes to separate the plasma, or, has resulted in the need for larger blood samples due to inefficient use of larger blood samples.
In most prior systems, clinical chemistry analyzers do not extract plasma or serum from blood as a part of the analysis process. It is done separately; either at the time of collection from the patient by collecting blood in a serum or plasma tube, or by spinning whole blood (or plasma) in a centrifuge before loading the plasma into the clinical chemistry analyzer. However, one known system as part of the analysis process extracts plasma from whole blood by centrifugation, spinning the blood for 2.5 min.
There are no commercial products that extract plasma from a drop of blood (fingerstick, 20-30 μL of blood). The system using centrifugation requires 100 μL of blood, 3-4 times more volume than a fingerstick can normally supply.
Extraction of plasma from blood in other microfluidic formats are done by centrifugation, the use of micropillars, or the Zweifach-Fung bifurcation Law.